article of faith

an article of faith (with sb) (a very basic belief not to be doubted; a deeply held belief; an unshakable belief in something without need for proof or evidence) — догмат веры; то, что принимается (или должно быть принято) на веру без доказательств; непоколебимое убеждение, не нуждающееся в доказательствах; что-л. само собой разумеющееся
something that someone believes very strongly without thinking about whether it could be wrong

Example 1: Socialism was an article of faith with his parents.

Example 2: It was an article of faith with Jill that everything she used should be recycled.

Example 3: It was an article of faith with this circle that women must free themselves.

Example 4: It was an article of faith with BB that a man should never shoot something unless he intended to eat it. Killing would otherwise represent a betrayal of one’s quarry.

Example 5: He concludes that it is “highly likely” that religion owes its origin to natural selection. He does not explain why; this conclusion seems to be an article of faith. (newyorker.com)

[gospel truth]